A number of systems currently exist for converting a pickup truck to a dump truck. A typical conversion kit employs a hinge to pivot the rear of the truck bed on the truck frame and an under body hoist to tilt the front of the truck bed to the dumping position. However, installation of these kits requires vehicle alteration which complicates installation and negatively impacts the safety and towing capacity of the altered truck.
U.S. Pat. No. 6,561,589 to Jones describes a dump truck hinge wherein the raising and lowering operation pivots the bed about a rear hinge connected in conventional fashion at and between the rear ends of the frame members. When this configuration is used to pivot a pickup truck bed, the hinge causes the tailgate to interfere with frame mounted equipment such as the exhaust system, spare tire carrier, rear bumper, tow hitch, and receivers. Thus, to convert the truck using this configuration, the frame mounted equipment must be removed completely or modified. Such modifications add considerable expense to dump truck conversions, lessen or eliminate the vehicle's towing capacity, and interfere with the aesthetic appearance of the truck itself.
Rather than discard the bumper, some conversions weld, or otherwise attach the bumper to the truck bed. U.S. Pat. No. 4,019,781 to Ray provides hinges that are fixedly attached to the underside of the hauling bed adapted for rotatable engagement with the rear of the truck frame. Extensions extending from the bumper are trimmed and, as so modified, are fixedly attached to hinge plate members. In this way, the bumper rotates with the hinge plate members as the bed is tilted. While this configuration provides a method of mounting the rear bumper, no provision is made to prevent the bumper or tailgate from interfering with the tow hitch and/or receivers. Furthermore, towing capacity and crash protection are limited by such bumper mounting modifications, hinges, hinge mounting, and hoist mechanisms as described by Ray.
When converting a pickup truck to a dump truck, space considerations make it impractical to use a separate hoist to elevate the rear of the dump body over the rear bumper and accessories. Other known methods of elevating the rear of a dump body are likewise not practical for pickup truck conversions. For example, U.S. Pat. No. 5,513,901 to Smith et al. describes a hoist mechanism having a moving instant center of body rotation. As the lift progresses a back link raises the rearward end of the dump body. In a short-body version of the apparatus, a forward transverse member is moved rearwardly toward the intermediate transverse member, shortening the hoist subframe. The hoist mechanism is preferably constructed with a mounting height of twelve inches. This raises the bed of a pickup truck higher than the cab when the bed is positioned in the lowered position and is aesthetically unappealing. In addition, because of space limitations, the short-body version requires more space than is available on a short bed pickup truck and thus is not feasible.
An object of the present invention is to provide a dump truck elevation device that can be installed on a pickup truck without alteration of the vehicle frame, rear bumper, bumper mounts, spare tire carrier, towing hitches or receivers, while preserving the aesthetic appearance of the truck itself.
Another object of the present invention is to provide a dump truck elevation device that permits dumping over the vehicle's bumper and other frame mounted accessories.
Another object of the present invention is to provide a dump truck elevation device that is easy to install.